SUMMARY OF THE INVENTION
The invention relates to a wrapping consisting of weldable film for bagpacks intended for receiving cut tobacco or the like, especially twistbags consisting of at least one film forming a pouch composed of a front wall and rear wall connected to one another laterally by means of lateral welding seams, and with a twist tab joined to the rear wall, the wrapping enclosing the bagpack in the form of a U and wrapping walls thus formed being closed on three sides by longitudinal and transverse welding seams. The invention also relates to a process and an apparatus for producing bagpacks of this type with a wrapping.
There are two known versions of bagpacks for tobacco. As regards the twistbag, the walls of a film blank are laid flat on one another and connected to one another laterally by means of lateral welding seams to form the pouch. Laterally projecting side tabs are usually obtained in the region of these lateral welding seams. The rear wall of the pouch is provided with an extension, in particular the twist tab.
A side-folding bag, which is the other version of a bagpack, is provided with a bottom wall and corresponding side walls in the region of the pouch for receiving the cut tobacco. Thus, the pouch, when filled, acquires an approximately cuboid shape. This bagpack too is provided with a twist tab.
To improve the preservation of aroma and moisture, bagpacks of the type mentioned above have recently been provided with an (outer) wrapping consisting of thermally weldable film. A bagpack with wrapping of this type is described in G.B. patent specification No. 12 11 247. A blank of weldable film is laid round the bagpack in the form of a U and closed so as to be leak-proof by means of a longitudinal welding seam and two transverse welding seams. This wrapping design is appropriate for twistbags, that is to say for relatively shallow bagpacks. Wrappings consisting of films are also already known for side-folding bags. Here, as, for example, in the case of cigarette packs, the blank is laid round the side-folding bag and closed, at least in the region of the side walls, when folding tabs are folded round in trapezoidal form (envelope folding). The production of a wrapping of this type involves a high outlay in terms of time and machinery. Moreover, the above-mentioned type of film folding is not completely leak-proof. Where bagpacks of this type (side-folding bags) are concerned, it is already known to attach a tear-open strip or thread to the wrapping.
The invention is concerned with wrappings for bagpacks of the twistbag type. In practice, the wrappings are produced by laying a continuous film sheet in the form of a tube round the twistbags conveyed in the longitudinal direction. The continuous film tube is provided in a conventional way with a continuous tube seam extending approximately in the centre of the topside and the rearside of the twistbag. The twistbags are located at a distance from one another inside the film tube. Transverse separating welding is carried out in the region of these interspaces, as a result of which the closed wrappings are formed.
In this production method, it is not possible to attach a desired tear-open strip. Furthermore, because of the production cycle the wrappings do not match the dimensions of the twistbags with sufficient accuracy. The latter have too much play within the wrapping.
The object on which the invention is based is, therefore, to propose a further development of the wrapping for twistbags, in which the abovementioned disadvantages are avoided, that is to say, in particular, a tear-open strip can be attached in a simple way and it is also possible to match the dimensions of the wrapping exactly to those of the twistbag. The object of the invention is also to propose a suitable production process and an apparatus for producing wrappings of this type.
To achieve the object stated first, the wrapping according to the invention is characterised in that a longitudinal edge strip having the longitudinal welding seam of the wrapping is folded round against one of the wrapping walls and is connected to the latter by means of (partial) welding.
Accordingly, the construction of the wrapping is such that, in an intermediate position of the pack, a laterally projecting longitudinal edge strip is formed. According to the invention, this is folded round against one of the wrapping walls before the transverse welding seams are made. When the transverse welding seams are made, with the folded-round longitudinal edge strip being included at the same time, the latter is fixed in the abovementioned position. A very close-fitting wrapping is consequently possible, because, particularly as a result of the folding round of the longitudinal edge strip, the wrapping is drawn closely up against the pack content.
The apparatus for attaching and completing the wrapping comprises a rotating turret with pockets, each receiving a twistbag with a wrapping. In a first pushing-in station, the twistbag is transported into a pocket of the turret along a (horizontal) feed track, at the same time carrying along and wrapping in the form of a U a blank provided for the wrapping. In this pushing-in station, excess lengths of wrapping which project from the pocket are then welded together to form the longitudinal edge strip with the longitudinal welding seam.
During further transport as a result of the rotation of the turret, the projecting longitudinal edge strip is first angled into an intermediate position and then, in a welding station, laid against the wrapping wall and welded laterally by means of the transverse welding seams.
According to the invention, the wrapping blank is severed from a continuous film sheet. This is provided (off-centre) with a continuous tear-open strip and a gripping tab.